Disturbance Suppression Considering Thrust Constant Fluctuation and Restoring Force of Flat Cable for Precise Force Control

Force sensorless control with voice coil motor (VCM) is thought to be challenging because its thrust constant fluctuation characteristic and the flexible flat cable connected to the moving coil degrade the estimation accuracy. Modeling methods of thrust constant fluctuation have been proposed in previous studies. However, these methods were time consuming, easily affected by friction, and did not consider cable disturbance. This article presents an identification and compensation methodology for nonlinear internal disturbances in a VCM to accomplish precise force control with a linear VCM stage. In this article, a novel compensator is constructed on basis of these deterioration mechanisms. To realize the compensator, the deteriorations had to be obtained. To that end, a novel approach to identify the parameter fluctuation and cable restoring force is developed, and the compensator is applied to sensorless force control. The proposed approaches are verified through experiments using the prototype of a linear VCM stage.